Synalpheus amintae, Ramos-Tafur & Franke-Ante, 2019

Ramos-Tafur, Gabriel E. & Franke-Ante, Rebeca, 2019, Synalpheus amintae sp. nov., a new species of sponge-dwelling snapping shrimp (Crustacea: Decapoda: Alpheidae) from Parque Nacional Natural Isla Gorgona, Pacific Coast of Colombia, Zootaxa 4646 (1), pp. 173-188 : 175-180

publication ID	https://doi.org/ 10.11646/zootaxa.4646.1.10
publication LSID	lsid:zoobank.org:pub:75F1031D-F96D-4BD5-AC9F-AA3AA4C2CE77
persistent identifier	https://treatment.plazi.org/id/039F878B-FFE6-FF9A-FF41-FEC2431EF827
treatment provided by	Plazi
scientific name	Synalpheus amintae
status	sp. nov.

Treatment

Synalpheus amintae View in CoL sp. nov.

( Figs. 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Holotype. 1 putative male or non–ovigerous specimen, CL 4.6 mm, TL 11.1 mm, La Gómez , (previously known as La Barra ), Parque Nacional Natural Isla Gorgona, 02°56’39”N, 78°12’08”W ( Fig. 1 View FIGURE 1 ); 28 Sep 1988; associated with unidentified encrusting sponge; coll. Rebeca Franke-Ante, FSBCI 138197 . GoogleMaps

Allotype. 1 post-ovigerous female, CL 5.7 mm, TL 13.6 mm, same data collections as holotype, FSBCI 138198 .

Paratypes. 1 post-ovigerous female, CL 5.1 mm, TL 12.8; 1 putative male or non–ovigerous specimen, CL 4.9 mm, TL 11.8 mm, same data collections as holotype, FSBCI 138199 .—1 post ovigerous female ( Fig. 5A View FIGURE 5 ), CL 7.1 mm, TL 17.2 mm, La Ventana , Parque Nacional Natural Isla Gorgona, 02°56’15”N, 78°12’21”W, 9 September 1987, associated with unidentified encrusting sponge; coll. Rebeca Franke-Ante, FSBCI 138200 .—1 ovigerous female ( Fig. 5B View FIGURE 5 ), CL ~4.1, mm, TL~ 12.3 mm, same data as previous, MIG GoogleMaps .

Comparative material examined. Synalpheus pectiniger Coutière, 1907: 1 male, CL 3.7 mm, TL 8.1 mm, 1 female, CL 3.9 mm, TL 9.3 mm, (both specimens with chelipeds missing), 67 Km SW off Egmont Key , west coast of Florida (27°37’00’’N, 83°28’00’’W), R/V Hernan Cortez, dredging, depth 37 m, 8 Jan 1965, coll. Robert F. Presley ( FSBCI 028667 ) GoogleMaps .— 1 female, CL 3.7 mm, TL 7.9 mm, net–trawl, same data as previous, 25 Jan 1967 ( FSBCI 028668 ) GoogleMaps .— 1 male, CL 3.6 mm, TL 9.1 mm, 56 Km SW off Sanibel Island , west coast of Florida (26°24’00’’N, 82°58’00’’W), R/V Hernan Cortez, net-trawl, depth 37 m, 13 Jan 1966, coll. Robert F. Presley ( FSBCI 028669 ) GoogleMaps .— 4 males, CL 3.5–4.0 mm, TL 7.8–9.4 mm, 6 females, CL 3.7–4.5 mm, TL 8.9–12.4 mm, offshore of Crystal River Power Plant, Citrus County, Florida, net-trawl, depth 3.7 m, 29 Mar 1969, coll. R. Parrish ( FSBCI 007672 ) .

Diagnosis. Carapace smooth, glabrous, with cardiac notch; pterygostomial margin projected but distally round- ed. Rostrum thin, tip slightly upturned, overreaching anterior third of visible portion of first antennular article, scarcely longer than tip of ocular teeth; ventral rostral process present, convex, not extending ventrally. Ocular hoods inflated, subtriangular, tips subacute, notches separating it from rostrum wide, U–shaped. Antennular pe- duncle slender, about 4.8 times as long as wide; first segment about 2.3 times as long as wide; second segment about 1.6 times, and third article about 2.1 times of first segment length. Stylocerite tapering distally, overreaching distal third of first antennular segment. Basicerite with small dorsal truncate tooth, and well–developed lateral tooth, tip reaching to middle of second antennular segment. Scaphocerite lacking lamella; lateral tooth overreaching distal margin of third antennular segment. Carpocerite slender, overreaching antennular peduncle by about length of third antennular segment. Tip of distal segment of third maxilliped furnished with eight non-acute curved spines; exopod almost reaching distal margin of antepenultimate segment. Merus of major cheliped with dorsal margin convex, distally projected, but no acute; chela ovoid; fingers occupying distal 0.25 of chela length; palm with distodorsal margin projected as rounded tubercle, ventrally armed with additional small acute tooth, slightly pointing downward; fixed finger or pollex very short, nearly undeveloped, distal tip not reaching to middle of dactylus length. Minor cheliped with merus elongated, dorsal margin convex with small rounded distodorsal projection; carpus cup shaped, with dorsodistal, and ventrodistal margins projected; chela elongated, fingers occupying distal third; palm smooth, ventral margin proximally excavated forming shallow groove; dorsodistal margin slightly projected, but non–acute; mesial palm with distal triangular projection; fixed finger ending distally bidentate; dactyl compressed, dorsal margin curved, with fringe of long setae on external margin; distal tip with double strong teeth; cutting surface of both fingers entire not excavated. Second leg with carpus five-segmented; first segment longer than following articles; ratio of carpal articles: 4: 1: 1: 1.1: 2.4. Third pereopod compressed; ischium and merus unarmed; carpus with ventrodistal spine; propodus ventral margin furnished with a row of seven movable spines, plus additional distal pair, just at dactylar articulation; dactylus biunguiculate, about of 0.2 of propodus length, ventral margin slightly swollen; dorsal unguis larger and slender than ventral unguis. Fourth and fifth pereopods similar to third, but slender. Abdomen smooth, glabrous; first somite of putative males with ventral margin anteriorly rounded, distally with acute projection; third and fourth somites with ventral margin acuminate; fifth somite with ventral margin rounded; sixth segment with posteroventral and posterolateral margins rounded, distodorsal margin covering slightly proximal margin of telson. Ovigerous and post–ovigerous females with all somites ventral margin rounded. Telson lateral margins slightly convex, tapering distally; dorsal surface equipped with four strong moveable spines, situated at 0.25 and 0.60 of telson length; posterior margin about 0.3 of anterior width, with small central projection, and two pairs of distal spines; anal tubercles well-developed, smooth, without setae. Uropods rounded distally; external uropod of putative males with five marginal acute teeth, ovigerous and postovigerous females with six–seven acute teeth, plus moveable spine, flanked by acute tooth; diaresis barely visible.

Description of holotype—putative male or non-ovigerous specimen— Carapace smooth, glabrous ( Fig. 2C View FIGURE 2 ), dorsally non–carinate, slightly compressed, ventral and dorsal margins convex; cardiac notch present; pterygostomial margin unarmed, evenly projected as rounded angle.

Rostrum thin, about 2.0 times as long as wide, broader at basal part, tip in lateral view slightly upturned ( Figs. 2 View FIGURE 2 A–C), overreaching proximal third of visible portion of first antennular article, furnished distally with short setae, and only little longer than tip of ocular teeth; ventral rostral process present, projected as small rounded convex carina. Ocular hoods inflated, broad at base, subtriangular, tips subacute, furnished with distal short setae, notches separating it from rostrum wide U-shaped. Eyes totally covered dorsally by orbital hoods, partially visible in lateral view.

Antennular peduncle slender, about 4.8 times as long as wide; first segment visible portion about 2.3 times as long as wide, ventral margin smooth, unarmed; second segment about 1.6 times of first segment length, and third article about 2.1 times of first segment length; all three segments ornate with distal marginal short setae ( Fig. 2A View FIGURE 2 ). Stylocerite broad proximally, tapering distally, with small rounded statocyst; tip bearing short setae, overreaching distal third of first antennular segment. Basicerite furnished with small dorsal truncate tooth, and well-developed lateral tooth, ending distally in acute tip, reaching to middle of second antennular segment. Scaphocerite lacking lamella, lateral tooth outer margin broadly concave, tip acute, noticeably shorter than carpocerite, but clearly overreaching distal margin of third antennular segment. Carpocerite slender, about 6.9 times as long as wide, overreaching antennular peduncle by entire length of third antennular segment.

Mouthparts not dissected, although observations under scope of those looks typical for Synalpheus . Third maxilliped overreaching distal end of carpocerite by about distal half of ultimate segment; exopod furnished distally with elongated setae, tip almost reaching distal margin of antepenultimate segment ( Fig. 2D View FIGURE 2 ). Antepenultimate segment slender, about 5.8 times as long as broad, dorsal margin slightly sinuous, ending distally in small rounded projection, furnished with few long setae; ventral margin slightly convex, furnished with long marginal setae. Penultimate segment about 1.6 times as long as broad or 0.2 of antepenultimate segment length, distally with bunch of marginal setae. Ultimate segment about 4.5 times as long as broad or 0.6 of antepenultimate segment length, tapering distally, with dorsal margin setose, without spines; ventral margin with few setae, and row of five movable spines, tip furnished with eight non–acute curved spines ( Fig. 2E View FIGURE 2 ).

First pair of pereopods dissimilar in shape and size. Left first cheliped or major cheliped ( Figs. 3 View FIGURE 3 C–D), with distal part of carpus reaching distal end of second antennular segment. Ischium ( Figs. 3 View FIGURE 3 A–B) about 0.5 times as long as broad, or 0.3 of merus length. Merus about 2.0 times as long as broad, dorsal margin smooth, moderately convex, projected distally as non–acute tooth; ventral margin concave, distal margin broadly rectangular; in mesial view ventrodistal margin ends also in non-acute rectangular projection. Carpus cup shaped, but noticeably elongated, with ventral margin projected, acute; dorsal margin rounded. Chela overall shape and cross-section ovoid, about 2.4 times as long as wide; dorsal and ventral margin smooth, convex, with fingers occupying distal quarter of chela length. Palm distodorsal margin ending as rounded projection, ventrally armed with additional small acute tooth, rather pointing downwards ( Fig. 3E View FIGURE 3 ). Fixed finger or pollex ( Figs. 3 View FIGURE 3 F–I), strongly truncate, very short, ending just at distal margin of fossa, forming small acute projection which do not match to distal half of dactylus. Fossa rounded, deep, allowing insertion of entire elongated plunger of dactylus, when fingers close. Dactylus compressed, dorsal margin broadly arcuate, with scarce setae, ending distally in corneous, somewhat truncate tip.

Right cheliped or minor cheliped with distal part of merus reaching distal end of third antennular segment. Ischium ( Figs. 4 View FIGURE 4 A–B) about of 0.75 as long as wide, or 0.2 of merus length, furnished with ventral setae. Merus elongated, about 3.2 times as long as broad, dorsal margin convex with small rounded distodorsal projection, furnished with couple of distal setae; ventral margin slightly convex, ornate with several setae. Carpus cup shaped, elongated, expanded distally, about 1.9 times as long as wide, or 0.6 of merus length, with dorsodistal, and ventrodistal rounded projections, furnished with few setae. Chela ( Figs. 4 View FIGURE 4 C–D) elongated, about 3.0 times as long as wide, with fingers occupying distal third; palm smooth, ovoid in cross-section; dorsal and ventral margins slightly convex, ornate with few long setae; ventral margin proximally excavated forming shallow groove; dorsodistal margin slightly projected, but non–acute, mesial palm with distal triangular projection. Fixed finger ending distally in double and acute strong teeth, distal one being longer, with tuff of setae on external, mesial and ventral margins. Dactyl compressed, dorsal margin curved, with fringe of long setae on external and dorsal margins, tip distally bidentate; cutting surface of both fingers entire, not excavate.

Second pereopod ( Fig. 2F View FIGURE 2 ) with distal end of merus overreaching distal end of first antennular segment when fully extended. Ischium about 3.6 times as long as broad, or 0.8 of the merus length, with scarce seta on ventral margin. Merus subequal in length to carpus, about 4.8 times as long as broad with few setae on ventral margin and a couple of setae on distodorsal area. Carpus five-segmented, first segment longer than following articles, about 4.4 of carpus length; ratio of carpal articles: 4: 1: 1: 1.1: 2.4. Chela robust, as long as sum of third, fourth and fifth carpal segments, with fingers as long as palm, ventral part of fixed finger and distal part of dactylus setose.

Third pereopod laterally compressed ( Fig. 2G View FIGURE 2 ), with distal end of carpus reaching distal end of second antennular segment when fully extend. Ischium unarmed, about 1.8 times as long as broad or 0.4 of the merus length. Merus about 3.3 times as long as broad, with dorsal margin convex, ornate with few short setae and two distal setae; ventral margin convex, setose, slightly tapering distally. Carpus about 2.2 times as long as broad or 0.4 of the merus length, with strong rounded distodorsal projection, and distoventral spine. Propodus about 4.3 times as long as broad, or 0.7 of the merus length, dorsal margin convex, ornate with setae, ventral margin furnished with row of seven movable spines plus additional distal pair, just at dactylar articulation. Dactylus biunguiculate, about of 0.2 of propodus length, ventral margin slightly inflated, dactylus of right leg with dorsal margin anomalous, displaying small notch or cut ( Fig. 2H View FIGURE 2 ), dactylus of left third leg with dorsal margin as usual, rounded without cuts ( Fig. 2I View FIGURE 2 ), dorsal unguis larger and slender than ventral unguis.

Fourth pereopod laterally compressed ( Fig. 2J View FIGURE 2 ) with distal end of merus overreaching pterigostomial margin when fully extend. Ischium unarmed, about 1.9 times as long as broad or 0.4 of merus length. Merus about 3.4 times as long as broad. Carpus about 2.4 times as long as broad or 0.4 of merus length, with distodorsal projection and distoventral spine. Propodus about 6.0 times as long as broad or 0.8 of merus length, ventral margin with a row of six movable spines, plus additional distal pair, just at dactylar articulation. Dactylus biunguiculate, about of 0.2 of propodus length, ventral margin slightly swollen.

Fifth pereopod laterally compressed ( Fig. 2K View FIGURE 2 ) with half of propodus overreaching pterigostomial margin when fully extend. Ischium unarmed, about 1.9 times as long as broad or 0.4 of merus length. Merus about 3.5 times as long as broad. Carpus about 4.3 times as long as broad or 0.4 of the merus length, with rounded distodorsal projection. Propodus about 5.5 times as long as broad or 0.7 of the merus length, ventral margin with two small movable spines broadly separated, and additional distal pair, just at dactylar articulation, distal half ornate with four rows of transverse combs of small setae. Dactylus biunguiculate, about of 0.2 of propodus length, ventral margin slightly swollen.

Abdomen smooth, glabrous ( Fig. 4E View FIGURE 4 ). First segment with ventral margin anteriorly rounded, distally with acute projection. Second segment broadly rounded. Third and fourth somites with ventral margin projected, acute. Fifth somite with ventral margin rounded. Sixth segment with postero–ventral and postero–lateral margins protruded, but rounded, distodorsal margin projected, rounded, covering slightly proximal margin of telson.

First pair of pleopods biramous, with endopod clearly reduced ( Fig. 5C View FIGURE 5 ); second pair of pleopods well developed ( Fig. 5D View FIGURE 5 ), without appendix masculine, but with appendix interna, ornate distally with cincinnuli ( Fig. 5E View FIGURE 5 ).

Uropods rounded distally ( Fig. 4F View FIGURE 4 ). Internal uropod setose. External uropod with five marginal acute teeth, plus acute moveable spine, flanked by acute larger tooth. Diaresis barely visible, extending from moveable spine to uropod mesial margin.

Telson 1.3 times as long as wide, with longitudinal medial groove and setae, lateral margins slightly convex, tapering distally. Dorsal surface armed with four strong moveable spines, tips projecting outside of telson lateral margins, situated at 0.25 and 0.60 of telson length. Posterior margin about 0.3 of anterior width, with small central projection, ornate distally with bunch of long setae, and two pairs of spines, inner pair larger, about double size of external pair. Ventral surface with anal tubercles well–developed, smooth, without setae.

Variation. Synalpheus amintae sp. nov. shows the following sexually–dimorphic features: ovigerous and postovigerous females look similar to putative males or non–ovigerous specimens, but the body and the chelipeds are larger. The entire ventral margin of the first abdominal segment of females is rounded, lacking acute projections, the third and fourth abdominal segments are broadly rounded ( Figs. 5 View FIGURE 5 A–B), the pleopods are also larger than in putative males, and the uropodal exopod is furnished with six to seven acute teeth before the movable spine and the flanking tooth.

Habitat. Synalpheus amintae sp. nov. is a subtidal species to 10 m. It was collected in the southern part of the Parque Nacional Natural Isla Gorgona, from two close locations, during extreme low tides—a phenomenon locally known as “puja”. This new species is an endosymbiont of unidentified encrusting sponges, which were found attached to rocks and surrounded by coralline sand. The porcellanid crab, Pachycheles sp., was found also using the sponge as shelter. Other crustaceans collected in situ, but not associated with the sponges, include the stomatopod Gonodactylus sp., the alpheid shrimps Alpheus cylindricus Kingsley, 1878 and Alpheus aequus Kim & Abele, 1988 , and the isopods Dynamenella sp. and Excorallana sp.

Etymology. This undescribed species of sponge–dwelling snapping shrimp is named in honor of Aminta, the mother of the first author.

Color in life. Cephalothorax olive green translucent with red–orange dots. Antennulae and antennae with transverse bands of orange and olive green. Major chela with external face green olive translucent, and two broad transversal bands of red–orange dots, dactylus proximally dark olive green, distally brown–mustard; mesial face olive green, dorsal margin yellow ochre. Minor cheliped, third maxillipeds and pereopods 2–5 green olive with red chromatophores. Abdomen, telson and uropods green translucent with red chromatophores. The coloration is more vivid in the post ovigerous females than in the ovigerous females (see Figs. 5 View FIGURE 5 A–B). Eggs dark brown.

Remarks. Worldwide the genus Synalpheus have more than 160 valid species, being the second–most speciose genus of Alpheidae ( Coutière 1909; Chace 1972; Banner & Banner 1966; 1975; Dardeau 1984; Ríos & Duffy 2007; Hultgren et al. 2010; De Grave & Fransen 2011; Anker et al. 2012, 2017; WoRMS 2019). The genus was subdivided in several artificial groups by Coutière (1909). One of the most diverse of these groups is the Synalpheus “Gambarelloides” species group with about 60 valid species described, a few of them living in the eastern Atlantic and Mediterranean ( Nardo 1847; Holthuis & Gottlieb 1958), and Indo Pacific (e.g. Banner & Banner 1966; 1975, Didderen et al. 2006), but this species group is remarkably more diverse in the western Atlantic, from the Gulf of Mexico, Florida, and Caribbean to Brazil ( Coutière 1909; Chace 1972; Dardeau 1984; Ríos & Duffy 2007; Hultgren et al. 2010; Anker et al. 2012).

Despite body size, diversity of habitats and ecosystems, apparently the genus Synalpheus is poorly represented in the eastern Pacific, with only 22 valid species described ( Coutière 1909; Abele 1975; Abele & Kim 1989; Wicksten 1983; 1989; 1994; Ríos 1992; Hermoso Salazar & Hendrickx 2005; Hermoso & Alvarez 2005; Hermoso-Salazar et al. 2005; 2008; Hermoso-Salazar & Solis-Weiss 2010; Anker et al. 2017), and only three species (including the new species described in this study) of the Synalpheus “ Gambarelloides ” species group are known from this area. It is necessary to mention that this is the first time, a species of this group is described near of the equatorial line, in the eastern Pacific, at the southern part of the zoogeographic Panamic Province. On the Pacific coast of Colombia only six species of Synalpheus have been previously reported ( Abele 1975; Lemaitre & Alvarez-León 1992; Prahl et al. 1978b; 1979, 1990, Wicksten 1983; 1989, Ramos 1995b).

The two previously described species of the Synalpheus “ Gambarelloides ” species group from the eastern Pacific, Synalpheus occidentalis Coutière, 1909 , and Synalpheus mulegensis Ríos, 1992 , both have been reported from the vicinity of Gulf of California and Baja California ( Coutière 1909; Ríos 1992; Hermoso-Salazar et al. 2008), and they are morphologically closely related to Synalpheus amintae sp. nov. The new species can be discriminated from them by the following set of characters: the rostrum in S. mulegensis is very short and slightly projected downward, lacking of ventral rostral process, the ocular teeth are as long as broad, and the notches separating it from the rostrum are of angular shape (see Ríos 1992: 11, Figs. 6A–B); the antennular peduncle is about 5 times as long as broad; the tip of stylocerite does not reach beyond the middle of first antennular segment; the lateral tooth of scaphocerite is short, only reaching to middle of second antennular peduncle; the basicerite lacking a dorsal tooth, and the tip of the lateral tooth reaches to the middle of the third antennular segment; the third maxilliped exopod is short, slightly overreaching the distal third of antepenultimate segment; the ultimate segment lacking distal spines, but instead bearing only a tuft of setae (see Ríos 1992: 11, Figs. 6G–H). In contrast for Synalpheus amintae sp. nov. the rostrum is longer, well-developed, with tip upturned, and furnished with concave ventral rostral process; the ocular teeth are broader than longer, and the notches separating it from rostrum are U-shaped. ( Fig. 2A View FIGURE 2 ); the antennular peduncle is about 4.8 times as long as broad; the tip of stylocerite overreaches the distal third of first antennular segment; the lateral tooth of scaphocerite is long, reaching the distal end of third antennular segment; the basicerite is furnished with small truncate dorsal tooth, and strong lateral tooth, with distal end reaching to middle of second antennular segment; the ultimate segment of third maxilliped is armed with eight curved spines ( Figs. 2 View FIGURE 2 D–E), and the long exopod reaches to distal end of the antepenultimate segment.

Additionally, the major cheliped of Synalpheus amintae sp. nov. ( Fig. 3 View FIGURE 3 ) exhibits the dorsal surface of merus, slightly convex; the dorsodistal protuberance of palm major chela is armed ventrally with a small acute tooth; the pollex or fixed finger is very short, ending almost at the distal margin of the fossa, forming a tiny acute tip; the external margin of uropodal exopod ( Fig. 4F View FIGURE 4 ) is armed with five small teeth in putative males or six to seven small teeth in females (not counting the moveable spine and, the acute tooth flanking the barely visible diaeresis). Distinctively, S. mulegensis has the major cheliped dorsal margin of merus broadly convex; the dorsodistal protuberance of major chela is unarmed, lacking additional teeth or spines; the pollex or fixed finger is short, but discernibly projected beyond the distal margin of the fossa, almost reaching to the middle of dactylus length (see Ríos 1992: 11, Figs. 6C–D). The external margin of uropodal exopod (see Ríos 1992: 11, Fig. 6I) is armed only with two small teeth (not counting the moveable spine and the flanking acute tooth); apparently lacking diaeresis.

Based on the figures of Coutière (1909, Fig. 34), Synalpheus occidentalis Coutière, 1909 was considered by Dardeau (1984: 45) and later by Rios (1992: 10) to be two different species, due to the variable range of morphological characters depicted. Nevertheless, Hermoso-Salazar et al. (2008) working with samples from the Gulf of California, did not find these variations relevant and considered this variation typical for this species, and concluded that the type material consisted of a single valid species. With this annotated clarification, S. occidentalis is categorized by having the ocular teeth longer than wide; the proportion of antennular peduncle is about 4.0 times as long as broad; the major cheliped fixed finger distal end reaches to or beyond the distal half of dactylus or moveable finger; the third pereopod dactylus ventral margin is smooth, without prominences; the dorsal spines of telson are situated between lateral margin and median line, and the anterior margin of telson is less than twice wider than distal margin. In contrast, the ocular teeth of Synalpheus amintae sp. nov. are wider than longer; the antennular peduncle is slender, about 4.8 times as long as broad; the major cheliped fixed finger distal end is truncate and does not reach to the middle of the dactylus length; the dactylus of third pereopod shows a tiny ventral prominence; the dorsal spines of telson are situated very close of lateral margin; and the anterior margin of telson is more than twice wider than distal margin.

Synalpheus pectiniger Coutière, 1907 View in CoL , from Gulf of Mexico, Florida Keys, Yucatan Peninsula, Bahamas, to Netherlands Antilles ( Coutière 1907, 1909, Chace 1972, Dardeau, 1984), Synalpheus disparodigitus Armstrong, 1949 View in CoL , from Domican Republic to Carriacou, Grenadine Islands ( Armstrong 1949; Chace 1972) and Synalpheus kuadramanus Hultgren, MacDonald & Duffy, 2010 View in CoL , from Curaçao ( Hultgren, MacDonald & Duffy 2010), are three species of the Synalpheus View in CoL “Gambarelloides” species group from the western Atlantic which share in common with Synalpheus amintae View in CoL sp. nov. the major cheliped fixed finger or pollex greatly reduced, notoriously shorter than dactylus. Notwithstanding their geographic distribution, they can be clearly discriminated by the following set of characteristics: S. disparodigitus View in CoL has the basicerite distal end reaching only to distal end of first antennular segment; the lateral tooth of scaphocerite is short, not reaching to distal end of third antennular segment; and the major chela is elongated, about 2.7 as long as wide (see Armstrong 1949, Fig. 6). In contrast, in Synalpheus amintae View in CoL sp. nov., the basicerite overreaches the distal margin of first antennular segment; the lateral tooth of the scaphocerite exceeds the distal end of third antennular segment; and the major chela is ovoid, about 2.4 times as long as broad.

The rostrum of Synalpheus pectiniger View in CoL is very short, not reaching the proximal third of first antennular segment; the basicerite lacks dorsal tooth, and the tip of lateral tooth reaches to distal part of second antennular segment, or sometimes almost of equal length as lateral tooth of scaphocerite; the distal tip of dactylus of minor chela is tridentate; the major chela palm is armed distally with protruding acute tooth directed upward, lacking of accessory ventral tooth; the telson have all four dorsal spines situated in the anterior half; the external uropod is armed with only one posterolateral tooth; the abdominal pleurae of non-ovigerous specimens is pointed ventrally (see Coutière 1909, Figs. 48–49; Dardeau 1984, Figs. 51–53). Instead in Synalpheus amintae View in CoL sp. nov. the rostrum is elongated, almost reaching the middle of first antennular segment; the basicerite is armed dorsally with small truncated tooth, and the lateral tooth is always shorter than lateral tooth of scaphocerite; the minor chela dactylus is distally bidentate; the major chela palm ends distally in a rounded tubercle with accessory small ventral tooth; the telson has only the proximal pair of dorsal spines situated in the anterior half; the external uropod is furnished with several teeth; and only abdominal pleurae of third and fourth segments of non-ovigerous specimens is somewhat pointed ventrally.

The stylocerite of Synalpheus kuadramanus reaches or slightly overreaches the distal margin of first antennular segment; the tips of rostrum and ocular teeth goes from the middle to the distal end of first antennular segment; the scaphocerite possesses a lamella, although it is reduced; the dactylus of major cheliped is square-shaped in lateral view; the tip of pollex of major chela reaches beyond the middle length of dactylus; the meri of major and minor chelipeds are armed distodorsally with acute tooth; and the uropodal exopod lacking teeth (see Hultgren et al. 2010, Figs. 10–13). Instead, in Synalpheus amintae sp. nov., the stylocerite does not reach to distal margin of first antennular segment; the rostrum and ocular teeth only reaches to the middle of first antennular segment; the lamella of the scaphocerite is absent; the dactylus of mayor cheliped is concave in lateral view; the tip of pollex of major chela is very short, not reaching the middle of dactylus length; the meri of major and minor chelipeds is armed distodorsally with rounded projection; and the uropodal exopod is furnished with teeth.

Finally, following the suggestions proposed by Anker et al. (2012: 86), Synalpheus amintae sp. nov. could be included as a “subsocial species” living in small groups, possibly as obligate sponge symbiont. In this particular case, Synalpheus amintae sp. nov. was found living in shallow waters on unidentified encrusting sponges.